The plot then flashes back to Martin's birth to Luke and his wife Sayna. Luke was the leader of a tribe of mice who are moving north to hopefully evade all enemies. The tribe lived an idyllic life for many seasons until Vilu Daskar, captain of the Goreleech, attacked the settlement and killed Sayna, as well as many others with his Sea Rogues. Luke vowed revenge upon Daskar and soon had an opportunity when Reynard Chopsnout, master of the Greenhawk, sailed in, hoping to fix his broken vessel. Luke killed him and captured the ship. Together with Vurg, Beau, and others, they sailed off. Martin, now older, wished to accompany his father, but Luke declined, giving Martin his sword, and the chance to name the ship, which is dubbed Sayna.

After sailing for a very long time, the ship is low on food. Luckily, they find an island filled with an abundant amount of food, but a strange creature attacks them for stealing his some of it. Luke discovers the creature is a hare, which is stranded on the island. The hare introduces himself as Beau, and he wishes to accompany them.

After a long period of tracking the Goreleech, the crew lands on an abandoned island. They find a pile of fruit lying mysteriously in front of them, believing it was some type of peace offering from natives, they eat. The fruit was actually drugged, a trap the vermin living there laid. The crew found itself in a cave to be sacrificed to a snake named Slariss. Luke managed to kill the beast, then threatened the leader of the savages in exchange for safe passage off of the island.

The Sayna follows the Goreleech to the Twin Islands, two islands very close together with a narrow waterway between them. The Goreleech ambushes the Sayna by ramming the it with a sharp horn on its bow. The Sayna is sunk and everyone on board is killed except Luke, Vurg and two other mice from the crew. Beau was believed to be dead, but survived. Luke, however, was captured by Daskar when the Sayna was destroyed. He befriended a black squirrel, Ranguvar Foeseeker, who also wanted her revenge. Luke was able to convince Daskar of a hidden treasure that only he could only steer to. Vurg and Beau sneaked aboard to free the slaves as Ranguvar and Luke killed foebeasts. Luke maneuvered to where he had trapped Daskar to one end of the ship, then steered it between two rocks, breaking it. He, Ranguvar, Daskar, and the entire vermin crew were drowned. The other half of the ship is lodged between the rocks.

Back in the present, Beau and Vurg presented Martin with a tapestry of his ancestor, which would eventually be expanded into one of the mouse himself. They all return to Redwall.

Meanwhile, back at the abbey, the others are hard at work on the construction. Martin allegedly chose to put down his sword and live a life of peace upon returning, and the book ends with a narration by Abbess Germaine.